Morphologic and Biochemical Characterization of Brain Injury in a Model of Controlled Blast Overpressure Exposure

Abstract

The proposed model of controlled nonpenetrating blast in rats demonstrates the critical pathologic and biochemical signatures of blast brain injury that may be triggered by cerebrovascular responses, including blood-brain barrier disruption, glia responses, and neuroglial alterations.

Animal models for the study of military-related, blast-induced traumatic brain injury

“…Intracranial measures in anesthetized rats demonstrated overpressure within the cerebral ventricles in the range of 30-40 kPa [31], and that blast effects upon intracranial pressure persisted for hours after exposure [24]. Long [28] reports that shock tube exposure at relatively higher levels (126-147 kPa) leads to cerebral hemorrhage, necrosis, cortical cell loss, gliosis, and widespread fiber degeneration, which is not reported in many studies with fluid percussion or control cortical impact injury; others also have reported little evidence of obvious focal cortical injury [25,31]. Compared to the methods described in A-C, the shock tube permits whole-body exposure, which is relevant to body effects from blast on neurological function, and studies related to the impact of armor or protective clothing are feasible [25,28].…”

“…Long [28] reports that shock tube exposure at relatively higher levels (126-147 kPa) leads to cerebral hemorrhage, necrosis, cortical cell loss, gliosis, and widespread fiber degeneration, which is not reported in many studies with fluid percussion or control cortical impact injury; others also have reported little evidence of obvious focal cortical injury [25,31]. Compared to the methods described in A-C, the shock tube permits whole-body exposure, which is relevant to body effects from blast on neurological function, and studies related to the impact of armor or protective clothing are feasible [25,28]. Finally, an obvious feature of the shock tube is that rodents sustain a closed head injury, and one can relate neuropathological and behavioral changes to physical characteristics such as peak pressure amplitude and exposure duration.…”

“…Several designs to induce an atmospheric shock wave have been developed and were described in recent reports [24][25][26]. Perhaps the most widely employed version is the shock tube utilized by researchers at the Walter Reed Institute for Army Research/Naval Medical Research Center [27][28][29][30].…”

On the prospective contributions of the shock physics community to outstanding issues concerning blast-induced traumatic brain injury

“…Rarefaction waves entering the tube from the open end and reaching the target after the initial overpressure loading should be accounted for or eliminated. Also, the use of the shock tube end jet to generate a decaying blast profile has been a popular approach [36,40,45], but such a set-up neglects that the blast flow field and ensuing dynamic pressure loading on the target are drastically changed even though the incident overpressure history may appear to match free-field scenarios. Another issue with conventional shock tube testing, which can alter the blast flow field significantly and exaggerate the loading on the target, is the ratio of tube blockage.…”

“…However, it is unfortunately not standard practice. While few researchers have purposely designed experiments to generate scaled-down exposure conditions [14,32,33] against small mammals, others expose animal models to blast parameters relevant to humans [27,[34][35][36][37][38][39][40][41][42][43]. Assuming mass scaling is relevant to bTBI, some of these exposures may effectively result in exposing an animal model to nuclear-sized blasts [29].…”